13 



cervical sclerites are termed by some writers the jugular 

 sclerites. 



The cervical sclerites are probably remnants of a segment the appendages 

 of which are modified to form the lower lip or labium. 



THE MOVABLE PARTS OF THE HEAD. 



Under this category are classed a pair of jointed append- 

 ages termed the antenna and the organs known collectively 

 as the mouth-parts. 



Antennae. Just cephalad of each compound eye there is 

 attached to the head a long, thread-like, many-jointed ap- 

 pendage. These are the antenna. Each antenna is situated 

 in a. depression which is known as the antennary fossa. 



Mouth-parts. 



Labrum. Although the labrum is a part of the skull it is 

 commonly regarded as one of the mouth-parts. 



Mandibles. Carefully remove the labrum. By doing 

 this there is exposed a pair of jaws which open by a meso- 

 lateral motion of each jaw. These are the mandibles. Each 

 mandible consists of a single short and thick piece, the distal 

 extremity of which is notched so as to form a series of teeth. 



Trochantin of the mandible. At the base of the man- 

 dible, between it and the gena, there is a small sclerite ; this 

 is the trochantin of the mandible. 



Remove the mandibles. This may be clone by separating 

 them with a pin and turning each one laterad until it breaks 

 from the head. 



Maxillae. By the removal of the mandibles there is ex- 

 posed a second pair of jaws which, like the mandibles, open 

 by a meso-lateral motion. These are the maxillce. Unlike 

 the mandibles the maxillae are very complicated organs. We 

 will return to them later. 



